Externally controlled hermetically enclosed electric switch



March 1,1966 MIACHON 3,233,344

EXTERNALLY CONTROLLED HERMETICALLY ENCLOSED ELECTRIC SWITCH Filed Nov. 50. 1962 FIG.4

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United States Patent France Filed Nov. 30, 1962, Ser. No. 241,380 Claims priority, application France, Dec. 5, 1961,

3 Claims. ((11.200-168) The present invention, which is due to Mr. Louis Miachon, relates to hermetic apparatus in which the internal mechanism comprises a moving member adapted to be displaced from the outside. The invention has for its object to provide an apparatus of the type in question which is of simple and robust construction and which can be made with extremely small dimensions, and it is applicable more particularly to electric switches of the type known as micro-switches, but it is to be understood that this reference is in no way limiting and that the invention may advantageously be employed with any other type of electrical or non-electrical apparatus (circuit breaker, thermostat, valve, etc.

It is known that great difficulties are encountered in constructing completely hermetic micro-switches which are capable of resisting considerable temperature variations. It is necessary first of all to ensure fluid-tightness of the component parts of a casing enclosing a complex mechanism. The control movement must be transmitted through the wall of the said casing without impairing its fluid-tightness, and in addition it is desirable that the conductive parts extending through the wall should be adequately insulated. In the known constructions, these various problems are solved by providing a deformable metal diaphragm soldered in position to permit the transmission of the movement, and by means of a multiplicity of other soldered assemblies, but this is done at the cost of obvious complications, of an excessive amount of waste and of a high price. Generally speaking, the known apparatus comprises a number of stages of soldered elements, so that the assembly tolerances of these various stages are frequency exceeded owing to the lack of precision in the welded joints.

The invention has for its object to obviate the aforesaid difiiculties. The apparatus according to the invention comprises essentially a base on which there is fitted by welding a cap having a deformable upper portion and integrally formed by the process known as chromizing, that is to say, by the formation of a compound of chromium and iron on a steel core which is thereafter removed by means of acid.

In a first embodiment, the cap is substantially cylindrical and its deformable portion consists of its upper end made in flat form with one or more concentric corrugations in the manner known in load-measuring cells. The centre of the said upper end may comprise a recess adapted to receive a member acting as a transmission means between the said end and the internal mechanism. The cylindrical portion may be formed with double thickness so as to have very great rigidity.

In another embodiment, the deformable portion consists of the top of the cylindrical portion of the cap, constructed in the form of a bellows having superposed circular corrugations.

The base is made of sintered alumina, porcelain or other material of the same type with a circular groove adapted to receive the lower edge of the cap, the said groove being metallised and receiving a soldering head which is brought into the liquid state at the time when the cap is positioned.

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The invention, its features and the advantages afforded thereby will be more readily understood from the accompanying drawings, which are given by way of example:

FIGURE 1 is a plan view of an electric microswitch according to the invention.

FIGURE 2 is a vertical section along the line 11-11 (FIGURE 1).

FIGURE 3 is a plan view of the base in the insulated condition, the posts supporting the internal mechanism being assumed to be cut away.

FIGURES 4 and 5 are sections similar to that of FIG- URE 2, but showing two variants of the invention.

The device illustrated in FIGURES 1 to 3 comprises a .base 1 made, for example, of sintered alumina or porcelain, into which three metal supporting posts 2, 3 and 4, respectively have been let during the moulding. The base 1, which is circular in the illustrated example, has in its upper face a circular groove 1a situated in the immediate neighbourhood of its periphery. It is also formed with an orifice 1b, in which there has been mounted in fluid-tight fashion, for example in the moulding before the firing (as in the case of the three posts), an appropriate duct 5 for exhausting the device after sealing, and for introducing into it an appropriate inert gas (nitrogen, argon, hydrogen, etc.

The post 2 supports the mechanism 6 of the switch, which mechanism is very diagrammatically illustrated in FIGURE 2 in the form of an appropriately stamped blade. Such mechanisms are well known, and therefore require no further description. The mechanism employed may be, for example, of the type comprising rolling springs or spring blades of appropriate configuration, these examples only being intended to give a cleaner idea. Mounted on the end of the mechanism 6 is the double movable contact 7, which moves between a first fixed contact 8 supported by the post 3 and a second fixed contact 9 indicated by broken lines in FIGURE 2 and supported by the post 4 situated in front of the sectional plane of the latter figure.

Mounted on the base 1 is a cap, which is denoted by the general reference 10. The said cap comprises a cylindrical wall 10a, of which the lower edge is engaged in the groove 1a and is secured therein by soldering, as will hereinafter be explained. The upper end of the cylindrical wall 10a is closed by a circular end member 10b formed with a concentric corrugation 10c intended to enable it to be deformed. The centre of the end member 10b comprises a portion 10d in the form of an inverted cylindrical cup, into which there is force-fitted a head 11 fast with a stem 11a which acts on the mechanism 6. The assembly 11-11a is preferably made of insulating material.

It will be appreciated that if the various component parts have been appropriately dimensioned, the mechanism 6 can, in the inoperative position, maintain the double movable contact 7 against the lower fixed contact 8, while when pressure is applied to the central portion 10a of the end member 10b the displacement of the stem 11a brings the mechanism 6 from one of its positions to the other, thus bringing the movable contact 7 against the upper fixed contact 9.

The cap 10 is formed by chromizing, that is to say, by forming on the surface of a steel core situated in an appropriate ammoniacal atmosphere a layer of a compound of chromium and iron and then cutting away one of the ends of the article obtained so as to expose the steel core and subjecting the latter to the action of acid until only the film of chromium-iron compound is left, which film can be given any thickness.

The connection between the cap 10 thus formed and the base 1 is obtained in the manner indicated in French Patent No. 1,240,552, applied for on July 25, 1959, in the name of applicants, for Improvement in Electric Switches. According to the said patent, the groove 1a has been metallised by any appropriate method. There has been deposited thereon an appropriate solder, whereafter the cap 10 has been positioned and the solder has been brought to the liquid state (for example by highfrequency heating), while at the same time the cap has been forced against the base in such manner that its lower edge penetrates to the base of the groove. After cooling, the cap is thus united with the base in an absolutely hermetic form and the assembly precision is limited only by the manufacturing tolerances of the cap and of the base, and is unaffected by the solder bead 12.

The invention thus provides a completely hermetic switch which can be mass-produced without any particular difliculty and at a very low cost. This device may be of very small dimensions, if desired, without its manufacture or its assembly thus being in any way complicated.

It will be noted that the cylindrical wall 10a of the casing 10 and the end member 1% of the latter must satisfy two contradictory conditions. The wall 10a must be completely rigid against compressive forces exerted on the device, while the end member 10b must behave in the manner of a resilient deformable diaphragm. It is to be noted that the cylindrical form of the wall 10a and the concentric corrugation 100 in the end member 10b tend to ensure that these conditions are fully satisfied, and that it is possible, if desired, to give the cordugation 10 a greater height or even to provide a plurality of corrugations such as 10c concentric to one another.

FIGURE 4 shows how the rigidity of the cylindrical wall may be increased when necessary. In this figure, the said wall 10a is of triple thickness, i.e., it has an external thickness of chromium-iron compound, an intermediate thickness of steel and an internal thickness of chromium-iron compound. This is readily achieved by carrying out the chromizing operation on a hollow core having a very thin lateral wall and then destroying the layer of chromium-iron compound which is formed on the inside face of the end portion of the said core and subjecting the steel of the core to the action of acid under conditions such that the said acid can remove the end portion of the core, which is exposed thereto over a wide surface, but scarcely attacks the thin cylindrical Wall of the latter, which is protected by the two concentric layers of the chromium-iron compound. In a modified embodiment, the initial lateral wall of the core may be sufficiently thin to be saturated with chromium throughout its mass, the final thickness then being substantially double that of the end portion.

FIGURE 5 shows another modified embodiment in which the deformability necessary to enable the internal mechansm of the switch to be actuated is afforded, not by the end member b, which is plane and consequently relatively rigid, but by corrugations 10c provided in the top of the cylindrical wall 10a. These corrugations con- 4 vert the top of the wall 10a into a form of metal bellows which is extremely deformable, even if the thickness of metal is relatively great.

It is to be understood that the foregoing description has been given only by way of example and that it in no Way limits the scope of the invention, of which the constructional details described may be replaced by any other equivalents without departing therefrom. The fluid-tight attachment of the supporting posts may be effected by soldering, as in the case of the lower edge of the cap. The internal mechanism of the device may be of any desired form, and it is to be noted that, as stated in the foregoing, the invention is applicable not only to hermetic electric switches, but also any other devices in which the same or similar problems arise.

I claim:

1. .An electric microswitch device, comprsing, in combination, a base of insulating material; a microswitch mechanism mounted on said base and including a control member; and a cap enclosing said switch mechanism and consisting of a single piece of metallic material, said cap including a substantially cylindrical outer wall having an open end sealingly secured to said base, and a transverse end wall integral with said cylindrical outer wall, at least one of said walls being yieldable in axial direction of said cap for actuating said control member, said cap completely enclosing said microswitch mechanism and forming with said base a fluid-tight envelope.

2. A device as set forth in claim 1, wherein said substantially cylindrical outer wall is shaped at least partly in the manner of a bellow with a series of circumferential corrugations so as to be yieldable in axial direction of said cap.

3. A device as set forth in claim 1, wherein said transverse end wall is formed with at least one substantially circular corrugation concentric with the axis of said cap so as to increase the ability of said wall to yield in axial direction of said cap.

References Cited by the Examiner UNITED STATES PATENTS 1,862,231 6/1932 McFarland 20441 2,509,227 5/1950 Gordy 74-18 2,728,826 12/1955 Lauder 200-67 2,800,438 7/ 1957 Stareck 204-41 3,015,010 12/1961 Greeson 200-153 3,030,465 5/1962 Roeser 200-168 3,054,879 9/ 1962 Soreng 200168 FOREIGN PATENTS 1,240,552 8/ 1960 France.

620,961 4/ 1949 Great Britain.

ROBERT S. MACON, Acting Primary Examiner.

BERNARD A. GILHEANY, KATHLEEN H. CLAFFY,

Examiners.

M. GINSBURG, Assistant Examiner. 

1. AN ELECTRIC MICROSWITCH DEVICE, COMPRISING, IN COMBINATION, A BASE OF INSULATING MATERIAL; A MICROSWITCH MECHANISM MOUNTED ON SAID BASE AND INCLUDING A CONTROL MEMBER; AND A CAP ENCLOSING SAID SWITCH MECHANISM AND CONSISTING OF A SINGLE PIECE OF METALLIC MATERIAL, SAID CAP INCLUDING A SUBSTANTIALLY CYLINDRICAL OUTER WALL HAVING AN OPEN END SEALINGLY SECURED TO SAID BASE, AND A TRANSVERSE END WALL INTEGRAL WITH SAID CYLINDRICAL OUTER WALL, AT LEAST ONE OF SAID WALLS BEING YIELDABLE IN AXIAL DIRECTION OF SAID CAP FOR ACTUATING SAID CONTROL MEMBER, SAID CAP COMPLETELY ENCLOSING SAID MICROSWITCH MECHANISM AND FORMING WITH SAID BASE A FLUID-TIGHT ENVELOPE. 